The present invention relates to internal combustion engines, and more particularly, to such engines in which it is desirable to be able to provide different types of valve gear train for different engine applications and/or markets and/or customers.
A conventional internal combustion engine of the type to which the present invention relates includes a cylinder block defining a plurality of cylinders. Each cylinder has a piston disposed therein, such that the region of the cylinder, above the piston, comprises a combustion chamber. It will become apparent to those skilled in the art that the present invention is applicable to practically any cylinder block configuration or type. For example, the invention could be utilized advantageously with a cylinder block of either the in-line configuration or the V-type configuration, and could be utilized with a cylinder block having any number of cylinders, the most common engine types being four-, six-, and eight-cylinder engines.
Conventional internal combustion engines also include a cylinder head assembly, such assemblies typically including the cylinder head and the head cover The typical cylinder head includes the appropriate number of intake and exhaust poppet valve assemblies, which are arranged in a pattern corresponding to the pattern of cylinders and combustion chambers defined by the cylinder block. Each of the poppet valve assemblies would include, by way of example only, a valve guide fixed within a guide bore defined by the cylinder head, a poppet valve which is reciprocable within the guide, a retainer to hold a valve return spring, and the valve return spring tending to bias the poppet valve toward its closed position, as is well know to those skilled in the art.
The conventional cylinder head also includes an appropriate valve gear train, operable to impart opening and closing motion to the intake and exhaust poppet valves. For example, the cylinder head may include integrally cast portions which support a cam shaft, wherein the cam shaft includes a plurality of cam lobes, each of which is disposed to impart pivotal movement to a rocker arm, such that the pivotal movement of the rocker arm provides the opening and closing motion of its respective engine poppet valve.
Internal combustion engines of the general type described above have been in widespread use for many years and have been considered quite satisfactory, in terms of engine performance. However, there are many situations in which the engine manufacturer has a particular base engine configuration (for example, an in-line six-cylinder engine block), wherein it would be desirable for the engine OEM to be able to provide the base engine block with any one of a number of different valve gear train types. For example, the engine OEM may utilize the base engine block in several different vehicle applications, or in several different geographic markets, wherein it would be desirable to be able to provide a series of valve gear train types of varying performance capability and therefore, of varying cost.
Unfortunately, each different valve gear train type has, in the past, necessitated a different cylinder head design, tailored to the particular valve gear train type, and the provision of (and casting, machining, etc.) a series of different cylinder heads for a single engine block adds substantially to the overall cost of each resulting engine type. This is true unless the production volumes of each engine type are quite large.
In addition to providing different valve gear train types, it may be desirable for the engine OEM to be able to provide, for each valve gear train type, several other options. For example, for a certain engine block, on those cylinder heads which are equipped with a center-pivot rocker arm, overhead-cam type valve gear train, the engine OEM may wish to offer the option of either individual fuel injectors or a common rail type fuel injection system. As another example, the engine OEM may wish, for the same valve gear train type, to be able to offer the option of either a conventional lubrication system (in which the head xe2x80x9csharesxe2x80x9d the engine oil with the block), or a sealed, self-lubricated head (in which the cylinder head assembly has its own oil supply and pressure source).
Accordingly, it is an object of the present invention to provide improved cylinder head assemblies which make it more economically feasible to provide several different valve gear train options for each particular base engine block.
It is a more specific object of the present invention to provide such improved cylinder head assemblies in which one part of the assembly remains common to all of the assemblies, and another part is different for each valve gear train type.
It is another object of the invention to provide an improved method of assembling a cylinder head assembly which will assist in achieving the above-stated objects.
It is another, more specific object of the present invention to provide such cylinder head assemblies wherein each valve gear train type may be provided with additional options, such as different fuel injection and lubrication options or arrangements.
The above and other objects of the invention are accomplished by the provision of an improved method of assembling a cylinder head assembly for use with a cylinder block of an internal combustion engine, the cylinder block defining a plurality of combustion chambers defining a chamber pattern.
The improved method comprises the steps of providing a cylinder head slab adapted to engage and be attached to the cylinder block and including a predetermined pattern of intake and exhaust poppet valve assemblies corresponding to the chamber pattern defined by the combustion chambers. The cylinder head slab is provided with a plurality of bolt holes defining a bolt hole pattern. The method includes providing a plurality of valve activation modules A and B in which each of said valve activation modules A and B comprises a housing and a plurality of valve actuators corresponding to the pattern of intake and exhaust poppet valve assemblies. The improved method further comprises selecting a module from the plurality of valve activation modules A and B, each of the valve activation modules defining a plurality of bolt holes which correspond with at least a major portion of the bolt holes of the bolt hole pattern defined by the cylinder head slab. Finally, the method comprises bolting the selected module A or B to the cylinder head slab.
In accordance with a further aspect of the invention, each of the valve activation modules A and B is a member selected from the group consisting of: a module having a valve gear train of the center-pivot rocker arm type, a module having a valve gear train of the camless type, a module having a valve gear train of the end-pivot rocker arm type, and a module having a valve gear train of the direct acting cam type.